Swipe to dismiss in Android Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What happens when you swipe an item in a RecyclerView with ItemTouchHelper?

Consider a RecyclerView with an ItemTouchHelper attached to enable swipe to dismiss. What is the expected behavior when the user swipes an item fully to the left?

A The item changes color but remains visible in the list.

B Nothing happens; the swipe gesture is ignored.

C The app crashes due to missing swipe callback implementation.

D The item is removed from the adapter and disappears from the list.

💡 Hint

Think about what swipe to dismiss means for a list item.

Swiping an item fully triggers the removal callback, which removes the item from the adapter and updates the UI to hide it.

❓ lifecycle

intermediate

When should you update your data source after a swipe to dismiss?

In a swipe to dismiss implementation, when is the best time to update the underlying data source to remove the swiped item?

A Immediately inside the onSwiped callback before notifying the adapter.

B After the RecyclerView animation finishes, using a delayed handler.

C Never update the data source; just hide the item visually.

D Only when the user confirms the deletion via a dialog.

💡 Hint

Consider the role of onSwiped callback in ItemTouchHelper.

The onSwiped callback is designed to notify you when an item is swiped. You should update your data source immediately there and notify the adapter to keep UI and data in sync.

🔧 Debug

advanced

Why does the app crash with IndexOutOfBoundsException after swipe to dismiss?

You implemented swipe to dismiss but after swiping an item, the app crashes with IndexOutOfBoundsException. What is the most likely cause?

Android Kotlin

override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
  dataList.removeAt(viewHolder.adapterPosition)
  recyclerView.adapter?.notifyItemRemoved(viewHolder.adapterPosition)
}

A The dataList is not synchronized with the adapter's data causing mismatch.

B You must call notifyDataSetChanged() instead of notifyItemRemoved().

C The adapterPosition changes after removal; notifyItemRemoved should use the old position before removal.

D You forgot to override getItemCount() in the adapter.

💡 Hint

Think about how dataList and adapter data relate.

If the dataList used in onSwiped is not the same list the adapter uses, removing from it causes mismatch and crashes. The adapter and data source must be consistent.

🧠 Conceptual

advanced

How does ItemTouchHelper.Callback control swipe directions?

In ItemTouchHelper.Callback, which method controls the allowed swipe directions for items?

A onSwiped() sets the swipe direction dynamically at runtime.

B onMove() returns the swipe direction as a boolean.

C getMovementFlags() returns flags indicating allowed drag and swipe directions.

D getSwipeDirs() is a method to disable swipe gestures.

💡 Hint

Look for the method that returns flags for movement.

getMovementFlags() returns a combination of drag and swipe directions as flags. This controls which gestures are enabled for each item.

❓ navigation

expert

What is the best way to restore a swiped item after dismissal?

After implementing swipe to dismiss, you want to allow users to undo the dismissal by restoring the item. Which approach is best?

A Immediately restore the item in onSwiped without removing it from the data source.

B Show a Snackbar with an Undo button that reinserts the item into the data and notifies the adapter.

C Reload the entire RecyclerView adapter data from the database on undo.

D Disable swipe to dismiss and use a long press to delete instead.

💡 Hint

Think about user experience and minimal UI disruption.

Showing a Snackbar with Undo is a common pattern. It lets users reverse the removal easily without reloading all data.